The aim of this project is to develop thermal blooming as a sensitive probe of electronic absorption. Thermal blooming refers to the lens effect created by the absorption of light with subsequent heating and local expansion. The effect is known to provide high sensitivity absorption measurements. Preliminary results obtained here suggest that two-laser techniques can provide sensitivity competitive with laser fluorimetry or photoacoustic spectroscopy. Thermal blooming is complementary to fluorescence and is simpler to apply in liquid media than photoacoustic spectroscopy. We propose to use time-resolved thermal blooming to monitor reaction rates. Several applications to enzymatic assay are proposed. We propose to use time resolved measurements in liquid chromatographic detector systems and as the detector system for wet analyzers. For rapid measurements a pulsed dye laser will be used to generate the thermal bloom and a He-Ne laser used to probe it. On a slower time scale a chopped argon ion or helium-cadmium will be used to generate the bloom and the helium-neon laser used to probe it. Further, because the measurements are made with two laser beams, they can be crossed and excellent spatial resolution obtained. It is proposed to develop a simple form of three dimensional microspectrophotometry employing this effect. It is suggested that the lasers needed are adequately inexpensive, reliable and easy to use, that thermal blooming spectroscopy can be employed by non-specialists.